This invention relates generally to medical apparatus such as catheters, needles, electrode leads and other devices which are inserted into a patient's body and more particularly to the provision of echogenic coatings on such devices to enhance their visibility during ultrasonic imaging.
Ultrasonic imaging in the medical field is widely used for a variety of applications. In addition to imaging physiological structures and tissue such as organs, tumors, vessels, and the like, it is often desirable for a physician or technician to have an image of a medical device which has been inserted into the tissue or passageway of a patient. A variety of approaches have been used to enhance ultrasonic imaging of devices by increasing the acoustic reflection coefficient of the devices. In U.S. Pat. No. 4,401,124 issued to Guess et al., the reflection coefficient of a biopsy needle is enhanced by the use of a diffraction grating disposed on the surface of the needle. A variety of mechanisms for enhancing the ultrasound image of a portion of a medical instrument are also disclosed in U.S. Pat. No. 5,289,831 issued to Bosley, U.S. Pat. No. 5,201,314 issued to Bosley et al. and U.S. Pat. No. 5,081,997, also issued to Bosley et al. These patents disclose catheters and other devices provided with echogenic surfaces including spherical indentations or projections in the range of 0.5 to 100 microns or fabricated of material incorporating glass spheres or high density metal particles in the range of 0.5 to 100 microns. The use of micro-bubbles introduced into polymers to provide echogenic catheter components is described in U.S. Pat. No. 5,327,891, issued to Rammler.